Your narrative of Gentiles stamping out Hebrew Christian Torah-observance may sound plausible because of historical situations of Jewish converts being caught in the crossfire between rabbinical Jews and Christians. However, the doctrines and practices of traditional Christianity were firmly established under the tutelage of the Jewish Apostles. It was Paul of Taurus who, not only criticized Greeks for Judaizing, but who castigated Peter himself for relapsing to the Mosaic dietary laws.
Anyway, that is entirely separate from Hagee’s denial that Christ came as reigning Messiah for the Jews. In the Gospels, John the Baptist, the Apostles, and Jesus Himself repeatedly testified to His coming as the Christ (also Messiah and Anointed One, which mean the same). The Messiah was prophesied to both suffer and reign when he came. No where does scripture support John Hagee’s teaching that He came first only to suffer, but would not reign until thousands of years later. Christ has reigned in the hearts of all Christendom for 2000 years and will continue to do so forever.
Your grasp of the New Testament is tainted by your Gentilization, I see. Where on earth did you get the idea that Peter withdrawing from table-fellowship with the Gentiles in Galatians had anything to do with the "Mosaic dietary laws"? As for Paul, if he himself wasn't keeping the Torah, then he was a liar and a purjurer when he claimed under oath before the Sanhedrin to still be a Pharisee (Acts 23:6)--read that, "Orthodox Jew." Why on earth do you pay attention to the writings of such a liar?
That, plus Acts 21, utterly destroys the basis for your anti-Judaic interpretation of Paul's letters. Either Paul was a hypocrite and a liar and should be expunged from the canon or you have grossly misinterpreted his writings. Paul was not saying that Jews should stop being Jews--he was defending the rights of Gentiles to remain Romans, Greeks, Americans, or whatever as followers of Israel's God and King.
But he never told any Jew not to continue keeping the Torah, circumcizing our sons, or following our traditions.
You and I agree that one who tells a Gentile that he must become a Jew in order to be saved is preaching another "gospel" and is anathema. What you fail to comprehend is that telling a Jew that they must become a Gentile in order to be saved is worse.